"After age 30, most men begin to experience a gradual decline in testosterone," says David Samadi, MD, chairman of the urology department at Lenox Hill Hospital in nyc.

Though testosterone levels never reach zero (as estrogen levels do in women during menopause), low testosterone levels men to experience symptoms like fatigue, low libido, and loss of muscle mass.

While low testosterone is more prevalent in older men, it may occur in younger guys as well. Fortunately, every one the causes of low testosterone in young guys are treatable, so if you experience these symptoms at any given age, there's no reason to dismiss it.

Causes of Low Testosterone in Younger Men

For younger guys, a fall in testosterone levels can be caused by some illnesses, including type 2 diabetes, diabetes, chronic liver or liver disease, COPD or other lung disease, or pituitary gland issues, according to Dr. Samadi.

Genetic causes of low testosterone in men include the ailments Klinefelter syndrome, Kallmann syndrome, Prader-Willi syndrome, and Myotonic dystrophy. Another disorder that could cause low testosterone is hemochromatosis, making the body shop too much iron.

"Low testosterone can also result when something happens, like trauma or steroid use, that prevents the testes from making the hormone," says Bruce Gilbert, MD, PhD, an adjunct clinical professor of urology and reproductive medicine at Weill Cornell Medical College and director of reproductive and reproductive medicine at the Smith Institute for Urology of their North Shore-LIJ Health System.

Additional causes of low testosterone in men younger than 50 contain adrenal gland tumors, HIV infection, and radiation therapy or chemotherapy for cancer.

Doctors categorize causes of low testosterone as secondary or primary.

"Primary hypogonadism stems from a problem in the testicles," Samadi says. "This could be from a developmental issue, injury to the testicles, or radiation or chemotherapy treatment. In secondary hypogonadism, the testicles are normal but function improperly because of a problem with the hypothalamus or pituitary gland."

If your blood test reveals low testosterone (usually defined as a level lower than 300 ng/dL), the doctor may treat you or refer you to a specialist, such as an urologist or endocrinologist.

Treatments for Low Testosterone in Younger Men

Not everyone with low testosterone needs treatment. "When it comes to treating low testosterone in older men, we generally reserve treatment for people who have symptoms, such as fatigue and low libido," Gilbert says.

In men who don't make the hormone in their testes because of a condition such as Klinefelter syndrome, or those who have lost their testes because of cancer, the only option is testosterone replacement therapy.

In these circumstances,"treatments are usually used only in the brief term, and if a doctor has close observation and understanding of the individual," Gilbert says.

An important consideration for younger men before getting treatment is fertility. "You don't want to give supplemental testosterone to men who are interested in being fertile since it can turn off sperm production," Gilbert says.

Once a young man goes off testosterone supplementation, there's a chance his sperm count will never return to what it was before he started. "Therefore, men of reproductive age should consider alternatives that might improve their testosterone in addition to preserve their sperm production," he says. One such alternative is a category of drugs known as selective estrogen receptor modulators (SERMs).

Other remedies for low testosterone include weight loss and other lifestyle modifications, like eating healthier and increasing exercise.

The bottom line, though, is that if you have low testosterone symptoms, it's important to see your doctor. Then, your doctor can rule out potentially more serious causes of your symptoms, such as high blood pressure or a thyroid problem, and offer treatment that can improve your power and high quality of life.